In a typical emulsion/dispersion manufacturing operation, gelatin concentrations are kept low (3% to 5%) during making and finishing. The 3 to 5% gelatin concentration is the minimum level required to suspend the silver halide. Levels of gelatin above this concentration interfere with nucleation and precipitation. When the emulsion/dispersion is eventually coated a much higher viscosity is required and this is achieved by raising the gelatin concentration up to approximately 15%. Historically, the best method to raise the gelatin concentration has been to add swollen gelatin (50% gelatin) or a gelatin solution (20% to 25% gelatin) in the late stages of finishing or in melting. These methods effectively raise viscosity but also significantly dilute the silver concentration due to the water component. It has been attempted to add dry gelatin (100% gelatin) directly to gelatin based emulsion/dispersion solutions, but clumping tends to occur and the undissolved clumps add to the nonuniformity of the emulsion/dispersion. The nondissolved gelatin contributes to variability as well as filter plugging, waste, and mechanical transfer problems. Dry gelatin has a water content of approximately 10%.
The present invention solves the problem of dry gelatin addition in a novel manner. The present invention accomplishes this feat in a simple, reliable, consistent manner while avoiding the clumping problem.